The present invention relates generally to computer hard drive disks manufactured using a sputtering process.
A hard disk drive (HDD) typically includes an array of storage disks from which and to which information is read and written. One commonly used method for manufacturing these disks is a sputtering process in which layers of material, e.g., aluminum and magnesium, are electrically deposited on a thinfilm glass substrate. During the sputtering process, each disk is held at its outer periphery at four points by two grippers. As the material is sputtered onto the disk, the grippers prevent it from being deposited on the outer edge of the disk at the four points of contact. Thus, a properly sputtered disk will have four manufacturing marks, i.e., shadows, around its outer periphery.
If a gripper is bent, it can leave a shadow on the surface of the disk instead of on the outer edge of the disk. Unfortunately, a shadow on the surface of the disk can expose the disk surface to corrosion. This corrosion can interfere with the read/write process resulting in improper operation of the HDD in which an improperly sputtered disk is installed. In light of the above problems, the present invention recognizes a need for a method to detect when a gripper is bent or otherwise misaligned.
A method for testing a computer disk includes sensing plural manufacturing marks on the disk. Based on the sensing act, a warning device is used to selectively indicate that the disk is defective. In a preferred embodiment, a quantity of manufacturing marks is compared to a predetermined value. If the quantity does not match the value, it is indicated that the disk is defective.
Preferably, the method further includes sensing a size of each manufacturing mark. Based on this sensing act, a warning device is used to selectively indicate that a disk gripper should be inspected. Moreover, the size of each manufacturing mark is compared to a predetermined threshold. If the size of the mark bears a predetermined relationship to the threshold, it is then indicated that the disk gripper should be inspected.
In a preferred embodiment, the disk is manufactured using a sputtering process and the manufacturing marks are shadows on the disk formed during the sputtering process. Specifically, the disk includes an outer edge and the shadows are located on the outer edge of the disk.
In another embodiment a system for testing computer disks includes a spindle and a disk mounted on thereon. The disk includes an outer edge and a sensor is placed in proximity to the outer edge of the disk to sense manufacturing marks formed thereon. A microprocessor is connected to the sensor and includes a program for determining a quantity of manufacturing marks formed on the edge of the disk.
In yet another aspect of the present invention, a method for testing a computer disk that is manufactured using a sputtering process includes rotating the disk at least three hundred and sixty degrees. As the disk is rotated, a quantity of manufacturing marks on the disk is sensed. If the quantity bears a predetermined relationship to a preselected value, it is indicated that the disk is defective.
The present invention will now be described, by way of example, with reference to the accompanying drawings, in which: